alt Hacker NewsThe problem with live patching is twofold.
First, you might not reload everything in memory, so it will be patched on disk but not in process.
Second, you have not tested that the system can boot to a functional system. Say you have done live patching for 5 years and never rebooted, and then you have a power loss or hardware failure/upgrade that takes the system down. When you try to bring it back up, it doesn't work. Which configuration change in the past 5 years caused that? Which backup do you use?
And, yeah, everything is hot swappable on VAX. Those machines also cost 6+ figures, and often require a service contract that includes a permanent on site tech.
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Which is moot, because of the system is important enough you'll have an automatic failover to another system running on standby
All this "we must reboot to test" is bullshit excuses by unqualified workers
>First, you might not reload everything in memory, so it will be patched on disk but not in process.
You design for this with generational tagged objects or something similar.
Yes, some things actually cost money, especially if they aren't easy to implement.
You patch it in memory and on disk. What you put on disk is the patch though, so when you restart, the original unpatched version is booted, and then the same live patch is applied. This is how Ksplice worked. It has the advantage that there isn't a config file in /etc to get changed out from under it, so the second problem did not apply.
And, yeah, everything is hot swappable on VAX.
Only the last generation or 2 of the highest end VAXen had any significant hot swap (VAX 9000/400 and later, which sold very poorly). The vast majority of VAX machines didn't. Even hot-swapping DSSI disks was at best iffy.
When someone whose been there talks about VAX 'high availability', they're usually talking about VAX/VMS clustering. Very cool and generally effective approach to the problem. That was one big issue with the end-game VAXen: clustering a couple of 6-figure mid-range machine was often considered a better solution than all-in on one 7- to 8-figure VAX 'mainframe'.
often require a service contract that includes a permanent on site tech.
I don't recall that being common with DEC service contracts. Most of the sites I know of that had dedicated DEC techs were either very large installs or had...other...drivers (e.g. tech had to have a TS clearance to work on the machines).